An X-ray tube assembly used for fluorescent X-ray analysis includes a cathode, anode target, cooling pipe, water conduit pipe, and jointing part (hereinafter, referred to as a joint) for joining the water conduit pipe and the cooling pipe to each other. The X-ray tube assembly is provided with a flow path of a coolant constituted of the cooling pipe, water conduit pipe, joint, and other structural members, the coolant being used to cool the anode target. The anode target is joined to a predetermined position on the outside of the structural member constituting the flow path. The water conduit pipe and the cooling pipe are respectively joined to the joint. The water conduit pipe is constituted of, for example, an inner pipe provided on the inside, and an outer pipe provided on the outside. A tip nozzle part of the inner pipe is arranged to eject the coolant in the direction to the position at which the anode target is placed. In this case, the cooling pipe is constituted of a first cooling pipe connected to the inner pipe through the joint, and a second cooling pipe connected to the outer pipe through the joint. In this X-ray tube assembly, the coolant is passed through the first cooling pipe, is sent to the inner pipe through the joint, is then passed through the flow path between the inner pipe and the outer pipe, and is discharged from the second cooling pipe through the joint.
In the X-ray tube assembly, electrons emitted from the cathode bombard the anode target, whereby the temperature of the anode target and a peripheral part thereof becomes high. The anode target and the peripheral part thereof are cooled with the coolant flowing through the flow path formed in their vicinities. On the wall surface inside a part of the flow path through which the coolant flows close to the position at which the anode target is placed, there is a possibility of subcooled boiling of the coolant or cavitation in the coolant flow occurring. Due to the subcooled boiling or cavitation, in the part of the flow path close to the position at which the anode target is placed, i.e., in the vicinity of the tip nozzle part of the inner pipe, bubbles form. Bubbles form at the periphery of the tip nozzle part of the inner pipe, and then the formed bubbles collapse (to generate a shockwave in the coolant), whereby the inner pipe can vibrate. When the fit clearance between the inner pipe and the joint is large, the vibration of the inner pipe becomes large, and furthermore there is a possibility of the noise becoming high.
As described above, due to the vibration incidental to collapse of the bubbles forming in the flow path because of the subcooled boiling, cavitation or the like, the water conduit pipe vibrates and comes into contact with the peripheral member, whereby there is a possibility of noise occurring.
The embodiment of the present invention has been contrived in consideration of these circumstances, and has it as an object thereof to provide an X-ray tube assembly having a structure configured to diminish vibration of the water conduit pipe in order to reduce noise.